Inlet orifice for continuous casting apparatus



9, 1966 R. M. PARKE. 3,264,592

INLET ORIFICE FOR CONTINUOUS CASTING APPARATUS Filed April 29, 1964 .5 E .00. m b g k .00/

k.) 0 I 1 I I I00 500 IIOU I500 Temp era lure C H/s Affom ey- United States Patent 3,264,692 INLET ORIFICE FOR CONTINUOUS CASTING APPARATUS Robert M. Parke, Coral Gables, Fla., assignor to General Electric Company, a corporation of New York Filed Apr. 29, 1964, Ser. No. 363,464

4 Claims. (Cl. 22--57.2)

This invention relates to an apparatus for the continuous casting of metals and more particularly to an improved orifice construction for those continuous casting apparatus in which elongated strip material is fed upwardly into a crucible containing molten metal to freeze additional metal thereon.

Strip processing utilizing a vessel or crucible having an inlet orifice located below the surface of fluid contained within the crucible requires minimal clearances between the surfaces of the strip and the surfaces of the means defining the inlet orifice to prevent fluid from escaping. The required minimal clearances in turn necessitate comparatively accurate control of strip feeding to preclude, as much as possible, contact with the walls of the inlet orifice. Further, the clearances are of such limited natures that the thermal expansion and thermal contraction characteristics of the ceramic materials from which the orifice defining means is constructed should closely match those of the input strip. However, in the present instant, the ceramics must further be essentially insoluble in molten steel since this is the material that is located within the crucible into which the strip is passing.

It is a principal object of the invention to provide improved orifice construction for continuous casting apparatus in which elongated strip steel is fed upwardly into a crucible containing molten metal to freeze additional metal thereon.

It is another object of the invention to provide an improved orifice construction for apparatus of the class described wherein provision is made for differing thermal characteristics of the input strip and the material from which the orifice is constructed.

Other objects and advantages of this invention will be in part obvious and in part explained by reference to the accompanying specification and drawings.

In the drawings:

FIG. 1 is a graph of the thermal expansion and contraction in inches per inch versus temperature for the ceramic, zircon;

FIG. 2 is a top elevation of a continuous casting apparatus according to this invention with portions of the inlet orifice construction broken away for purposes of clarity;

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 2;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 2; and

FIG. 5 is a partial perspective view of an inlet orifice construction according to the present invention.

Generally, the improved inlet orifice construction comprises comparatively elongated side walls constructed of high fired or high density zircon and end walls which are operatively associated with the elongated side walls and are comparatively shorter, which end walls are constructed of a material that can be readily abraded or machined by the passage of steel strip through the inlet orifice upwardly into the molten metal contained within a crucible.

It will readily be appreciated that the ceramic materials that are brought into contact with molten metals and especially with molten steel, must meet stringent requirements, particularly in that they do not react with or be seriously dissolved by the metal. Also, they must be thermally stable and strong to resist cracking, breaking, spalling and the like. I have found that zircon, which is zirconium silicate, ZrSiO is admirably suited 3 ,264,692 Patented August 9, 1966 ice for contact with molten steel, both from the standpoint of relative insolubility and from the standpoint of mechanical strength characteristics over severe thermal cycling conditions.

However, as shown by the graph in FIG. 1, there is a hysteresis effect in the expansion and contraction which occurs when zircon is thermally cycled between room temperature and about 1500 C. The effect is largely an indirect result of the thermal dissociation of zircon into zirconia and silica, viz. ZrSiO ZrO +SiO the zirconia then accounting for the predominant amount of volumetric change. Referring again to FIG. 1, the curve 10 represents the expansion of zircon on heating and clearly shows that it undergoes a drastic change in expansion characteristics at around 1100 0., when substantial amounts of zirconia are present. Further, it will be noted that a similar, although not precisely identical, change in contraction characteristics happens when the material is cooled, as shown by curve 11.

Referring to FIG. 2, numeral 15 represents a crucible for holding the molten metal. In the center and at the bottom of the crucible can be seen the inlet orifice 16 and the means 17 which define the orifice. This means comprises elongated side walls 18 which taper downwardly away from orifice 16 and end walls 19 which define the lateral limits of orifice 16. The orifice defining means is also provided with tapered faces 20 which serves to assist holding the orifice means 17 in its proper geometric location.

FIGS. 3 through 5 illustrate in more detail the physical construction of the orifice defining means. Referring to FIG. 3 specifically, the strip 25 moves upwardly through the orifice 16 with only a very minimal amount of clearance 26 between its lateral edges and the edges of end walls 19. If both the end walls and the side walls were constructed of high fired or completely dense zircon, the space 26 would disappear when strip 25 was started upwardly through the crucible and it would gall or seize against walls 19 and completely stop further movement of the strip. The disappearance of space 26 is caused by the cooling effect which strip 25 has on the orifice 16, the cooling causing a large contraction of the zircon (FIG. 1).

The orifice defining means may be constructed of two principal halves 30 and 31 (FIGS. 4 and 5) which constitute the side walls 18. The end Walls 19 are then held in position between the two principal halves by means of pins 32. Obviously, any other suitable means for joining these various pieces into one integral unit may be equally effective.

I have now found that seizing of metal strip 25 within the inlet orifice can be effectively prevented by constructing the end walls 19 of a material which is comparatively softer than the high density zircon from which the side walls 18 are constructed. While the side walls 18 are high fired to a density of not less than 3.7 gm./cm. a density of up to about 3.8 gm./cm. has been found to be more desirable. On the other hand, I have now found that the end walls 19 can advantageously be constructed of ziron which has been low fired to a density ranging from about 3.45 to 3.55 gm./cm. This low firing pro duces a body which in terms of macro-hardness is softer than the side Wall zircon, and in fact is friable to the extent that a mild steel (SAE 1010) input strip 25 will readily abrade away any wall material that it comes into contact with. An additional material which is applicable under the operating conditions present in this type of apparatus is graphite. 'l he graphite is slightly more soluble in molten steel than is zircon but the solubility rate is not sufiiciently large to constitute an insurmountable difiiculty.

pansion ceases to coincide with that of the steel input strip, the strip will contact the surfaces of end walls 19 and rather than becoming lodged, will merely abrade away enough of the wall surfaces so that free passage onwardly into the interior of crucible 1-5 readily occurs.

Although the present invention has been;described in connection with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and the appended claims.

What I claim as new and desire to sec-uretby Letters Patent of the United States is:

1. Ina continuous casting apparatus in which elongated strip steel is fed upwardly through an inlet orifice into a crucible containing molten metal to freeze additional metal thereon, the combination comprising means defining an inlet orifice having side walls and endwalls which together define an inlet opening, said side walls being constructed of zircon having a density of not less than about 3.7 gnL/cm. and said end walls being :constructed of a material selected from the group consisting of zircon having [a density no greater than about 3.55 gm./cm. and graphite.

2. An inlet orifice asv defined in claim 1 wherein the: density. of the zircon in said end walls is in the: range, of

from aboutSAS- to 3.55 gn1./cm.

3..'An inlet orifice as defined'in claim 1 wherein said inlet opening is ofgenerally rectangular cross-sectional configuration."

4. In acontinuous casting apparatus in which elongated strip steel is fed upwardly through an inlet orificev intoa crucible containing moltenrnetal to freeze additional metalthereon, the combination comprising means defining an-inlet orifice having side walls and end walls together .defining'an inlet; opening of generally rectan-' gular cross-sectional configuration, said side walls being constructediof zircon having a density of from about 3.7

to 3.8 -gm./cm. and said .end walls-being constructed of a material selected from the :group consisting of zircon having densities of firom,:about 3.45 to 3.55 gin/ cm. and graphite.

J. SPENCER OVERHOLSE-R,Primary Examiner. R. S. ANNEAR, Assistant Examiner. 

1. IN A CONTINUOUS CASTING APPARATUS IN WHICH ELONGATED STRIP STEEL IS FED UPWARDLY THROUGH AN INLET ORIFICE INTO A CRUCIBLE CONTAINING MOLTEN METAL TO FREEZE ADDITIONAL METAL THEREON, THE COMBINATION COMPRISING MEANS DEFINING AN INLET ORIFICE HAVING SIDE WALLS AND END WALLS WHICH TOGETHER DEFINE AN INLET OPENING, SAID SIDE WALLS BEING CONSTRUCTED OF ZIRCON HAVING A DENSITY OF NOT LESS THAN ABOUT 3.7 GM./CM.3 AND SAID END WALLS BEING CONSTRUCTED OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF ZIRCON HAVING A DENSITY NO GREATER THAN ABOUT 3.55 GM./CM.3 AND GRAPHITE. 